Vacuum cleaners are known in which the brush is movable in the nozzle opening. For example the brush can be rotatable or movable back and forth. A brush of the latter type is described and shown in U.S. Pat. No. 1,336,760. A horizontally mounted eccentric disc causes the movement forwards and backwards of the brush whereby the tips of the brush bristles move on the work surface all the time, i.e. in the same horizontal plane as this surface. Thus, the object of the brush device shown and described in the aforesaid patent is to work on a soft surface, such as a short-piled rug, so that dust is stirred up by the brush and conducted by the suction air to a dust collector. It has been found, however, that the dust absorbing capability of this device is not sufficient to satisfy the present requirements in this respect. This is due to the fact that instead of being worked up from the rug the dust is forced into it by the brush.